Photoluminescence intensity enhancement of a silicon quantum dot solution was investigated using in situ photoluminescence/dark-field microscope spectrometer. The intensity was enhanced by Medusa-type silver particle, composed of a sphere 760 nm in diameter and many nanochains. The enhancement factor (EF) was carefully estimated, based on various corrections and finite-difference time-domain (FDTD) calculations. The EF was changed from 33 to 42000. Spectroscopic and FDTD analyses proved valuables to evaluate local enhancement effect. Wavelength dependences of EF and scattering spectrum indicated that the enhancement is attributed to the electric field localized on particle, given by not photoluminescence light but excitation light. (C) 2013 Elsevier B.V. All rights reserved.